Dinitriles are common feedstocks to the chemical, pharmaceutical, and agrochemical industries. Through hydrogenation they can be converted to diamines and/or aminonitriles, which are used in or as polymer intermediates, surfactants, chelating agents, and chemical synthesis intermediates. As a particular example, adiponitrile can be converted to 6-aminocapronitrile and/or hexamethylenediamine by hydrogenation. Hexamethylenediamine is an intermediate in the production of Nylon 6,6. 6-aminocapronitrile can be used as an intermediate in the production of Nylon 6.
Traditional methods of producing hexamethylenediamine include hydrogenation of adiponitrile over a reduced iron oxide or cobalt oxide catalyst at high pressures and temperatures. U.S. Pat. No. 6,110,856 describes the use of cobalt and iron based catalysts in a process for the hydrogenation of adiponitrile to a mixture of aminocapronitrile and hexamethylenediamine. The process does not produce aminocapronitrile with high selectivity, yielding 37% aminocapronitrile at 75% adiponitrile conversion. Low-pressure processes are known for the simultaneous production of aminocapronitrile and hexamethylenediamine. U.S. Pat. No. 5,151,543 describes the hydrogenation of dinitriles, including adiponitrile in the presence of a solvent. U.S. Pat. Nos. 6,258,745, 6,566,297, 6,376,714 and WO 99/47492 and WO 03/000651 A2 all describe the hydrogenation of dinitriles to aminonitriles in the presence of selectifying agents for low pressure reactions, i.e., 1 less than about 13.89 MPa (2000 psig).
For simultaneous production of aminonitrile and diamines, it would be advantageous to employ commercial equipment that is currently used for hexamethylenediamine production and that operates at high pressures, i.e. greater than 13.89 MPa (2000 psig). Additionally, it would be advantageous to operate these processes with increased selectivity to aminocapronitrile than is possible under operating conditions taught in the art.